1. Field of the Invention
The present invention relates to a shield support for underground mining having a slider and a roof bar between which at least one ram is arranged.
2. The Prior Art
Shield supports of this type have the task in underground mining of supporting the roof and of preventing too early a collapse of the roof in that it is supported by the roof bar. It can, however, occur in practice that parts of the roof have already collapsed before the roof bar of the shield support was able to be set for support so that a burst arises in the roof. If the shield support subsequently advances and if the rams are then, as usual in part, are automatically set to an adjustable setting pressure, the roof bar would be pressed into the burst, whereby not only the roof bar, but the whole shield support might be damaged. It is furthermore sensible for the avoidance of further bursts to support the roof as close as possible to the coal face. This in turn means that the roof bar of the shield support should be held in the direction of the interface between the roof and the coal.
It is therefore the object of the invention to improve a shield support of the initially named kind such that damage to the shield is prevented and an ideal support of the roof is ensured.